[PATCH 02/15] ARM: limit OABI support to StrongARM CPUs

[Arnd Bergmann]

From: Arnd Bergmann <arnd@xxxxxxxx>

As discussed on the mailing lists, there is no way to build OABI userspace
binaries any more since gcc-4.8, and now support is also getting dropped in
binutils, which will make it impossible to build pure OABI kernels at some
point in the future.

I found no evidence of anyone still sing OABI userspace on embedded systems
that keep getting kernel updates, but there are a few desktop-class machines
that date back to the 1990s using Intel StrongARM processors that were
supported by old versions of Debian, Red Hat or the official Corel
Netwinder distribution.

Add a much stricter Kconfig dependency for both native OABI and OABI_COMPAT
enabled kernels, only allowing either of them to be selected when building
a kernel that targets a StrongARM based machine.

Link: https://lore.kernel.org/lkml/2831c5a6-cfbf-4fe0-b51c-0396e5b0aeb7@xxxxxxxxxxxxxxxx/
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
 arch/arm/Kconfig                       | 14 +++++++-------
 arch/arm/configs/am200epdkit_defconfig |  1 -
 arch/arm/configs/axm55xx_defconfig     |  1 -
 arch/arm/configs/footbridge_defconfig  |  2 +-
 arch/arm/configs/neponset_defconfig    |  2 +-
 arch/arm/configs/versatile_defconfig   |  1 -
 6 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index f8f127650ace..54f5cc12dea4 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1161,8 +1161,7 @@ config ARM_PATCH_IDIV
 	  code to do integer division.
 
 config AEABI
-	bool "Use the ARM EABI to compile the kernel" if !CPU_V7 && \
-		!CPU_V7M && !CPU_V6 && !CPU_V6K && !CC_IS_CLANG
+	bool "Use the ARM EABI to compile the kernel" if CPU_SA110 || CPU_SA1100
 	default y
 	help
 	  The Arm EABI is the default ABI on all modern Linux
@@ -1172,9 +1171,13 @@ config AEABI
 	  Everyone should enable this, as support for OABI user space
 	  was dropped in gcc-4.8 and most distributions after ca. 2013.
 
+	  Support for OABI mode will be removed from the kernel
+	  once Intel StrongARM CPUs are phased out.
+
 config OABI_COMPAT
 	bool "Allow old ABI binaries to run with this kernel (EXPERIMENTAL)"
 	depends on AEABI && !THUMB2_KERNEL
+	depends on CPU_SA110 || CPU_SA1100
 	help
 	  This option preserves the old syscall interface along with the
 	  new (ARM EABI) one. It also provides a compatibility layer to
@@ -1187,11 +1190,8 @@ config OABI_COMPAT
 	  selected, since there is no way yet to sensibly distinguish
 	  between calling conventions during filtering.
 
-	  If you know you'll be using only pure EABI user space then you
-	  can say N here. If this option is not selected and you attempt
-	  to execute a legacy ABI binary then the result will be
-	  UNPREDICTABLE (in fact it can be predicted that it won't work
-	  at all). If in doubt say N.
+	  Support for OABI_COMPAT will be removed from the kernel
+	  once Intel StrongARM CPUs are phased out.
 
 config ARCH_SELECT_MEMORY_MODEL
 	def_bool y
diff --git a/arch/arm/configs/am200epdkit_defconfig b/arch/arm/configs/am200epdkit_defconfig
index 22397d45f4a0..55c5c08a5f96 100644
--- a/arch/arm/configs/am200epdkit_defconfig
+++ b/arch/arm/configs/am200epdkit_defconfig
@@ -7,7 +7,6 @@ CONFIG_EXPERT=y
 # CONFIG_ARCH_MULTI_V7 is not set
 CONFIG_ARCH_PXA=y
 CONFIG_ARCH_GUMSTIX=y
-# CONFIG_OABI_COMPAT is not set
 CONFIG_CMDLINE="console=ttyS0,115200n8 root=1f01 rootfstype=jffs2"
 CONFIG_MODULES=y
 CONFIG_MODULE_UNLOAD=y
diff --git a/arch/arm/configs/axm55xx_defconfig b/arch/arm/configs/axm55xx_defconfig
index 39b06d59d87a..9d14b987ee94 100644
--- a/arch/arm/configs/axm55xx_defconfig
+++ b/arch/arm/configs/axm55xx_defconfig
@@ -38,7 +38,6 @@ CONFIG_PCIE_AXXIA=y
 CONFIG_SMP=y
 CONFIG_NR_CPUS=16
 CONFIG_HOTPLUG_CPU=y
-CONFIG_OABI_COMPAT=y
 CONFIG_HIGHMEM=y
 CONFIG_ARM_APPENDED_DTB=y
 CONFIG_ARM_ATAG_DTB_COMPAT=y
diff --git a/arch/arm/configs/footbridge_defconfig b/arch/arm/configs/footbridge_defconfig
index 589b7b1df8c6..e8bf9847d35d 100644
--- a/arch/arm/configs/footbridge_defconfig
+++ b/arch/arm/configs/footbridge_defconfig
@@ -9,9 +9,9 @@ CONFIG_ARCH_MULTI_V4=y
 CONFIG_ARCH_FOOTBRIDGE=y
 CONFIG_ARCH_EBSA285_HOST=y
 CONFIG_ARCH_NETWINDER=y
+# CONFIG_AEABI is not set
 CONFIG_FPE_NWFPE=y
 CONFIG_FPE_NWFPE_XP=y
-# CONFIG_AEABI is not set
 CONFIG_MODULES=y
 CONFIG_PARTITION_ADVANCED=y
 CONFIG_ACORN_PARTITION=y
diff --git a/arch/arm/configs/neponset_defconfig b/arch/arm/configs/neponset_defconfig
index a8833b2ce335..7a7b6a896f85 100644
--- a/arch/arm/configs/neponset_defconfig
+++ b/arch/arm/configs/neponset_defconfig
@@ -6,12 +6,12 @@ CONFIG_ARCH_MULTI_V4=y
 CONFIG_ARCH_SA1100=y
 CONFIG_SA1100_ASSABET=y
 CONFIG_ASSABET_NEPONSET=y
+# CONFIG_AEABI is not set
 CONFIG_ZBOOT_ROM_TEXT=0x80000
 CONFIG_ZBOOT_ROM_BSS=0xc1000000
 CONFIG_ZBOOT_ROM=y
 CONFIG_CMDLINE="console=ttySA0,38400n8 cpufreq=221200 rw root=/dev/mtdblock2 mtdparts=sa1100:512K(boot),1M(kernel),2560K(initrd),4M(root) load_ramdisk=1 prompt_ramdisk=0 mem=32M noinitrd initrd=0xc0800000,3M"
 CONFIG_FPE_NWFPE=y
-# CONFIG_AEABI is not set
 CONFIG_PM=y
 CONFIG_MODULES=y
 CONFIG_MODULE_UNLOAD=y
diff --git a/arch/arm/configs/versatile_defconfig b/arch/arm/configs/versatile_defconfig
index 8e89debb5a5b..bb9eb9ccbbde 100644
--- a/arch/arm/configs/versatile_defconfig
+++ b/arch/arm/configs/versatile_defconfig
@@ -6,7 +6,6 @@ CONFIG_LOG_BUF_SHIFT=14
 CONFIG_BLK_DEV_INITRD=y
 # CONFIG_ARCH_MULTI_V7 is not set
 CONFIG_ARCH_VERSATILE=y
-CONFIG_OABI_COMPAT=y
 CONFIG_CMDLINE="root=1f03 mem=32M"
 CONFIG_FPE_NWFPE=y
 CONFIG_VFP=y
-- 
2.39.5